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3D lattice structures: Design elements and mechanical responses

Lattice structures are repeating patterns that, when connected, form three dimensional shapes. In an additive manufacturing context, compliant lattice structures open up exciting product design possibilities as designers harness 3D printing technologies to create previously ‘unmakeable’ shapes and parts. When made from elastomers, 3D printed lattice structures are highly deformable and their mechanical properties allow for them to be tuned over a wide range of responses, and used in a spectrum of industries.

 

However, designing compliant 3D lattice structures requires manufacturing expertise – not to mention the right software tools. At Fast Radius, we’ve designed and tested 3D printed lattice structures for a vast range of different products and applications. We’ve used computer simulation to create a large library of data, classifying different lattice structures, and their mechanical properties.

 

If you’re searching for the right type of 3D lattice structure for your manufacturing project, it’s vital that you understand how different design elements will affect the mechanical responses of your finished part. With that in mind, to help you explore your project’s additive manufacturing potential, we’ve put together a short guide to key 3D lattice design elements – along with four examples of compliant lattice structures selected from our library.

Key design elements for elastomer 3D lattice structures

Body centered lattice

 

Elastomer 3D lattice structure projects commonly consider some or all of the following four design elements:

 

Geometry: The geometry of a lattice refers to the physical size and shape of its components – and how their pattern is arrayed throughout the structure of a part. Where they are repeated, single units within the structure of a lattice are known collectively as unit cells – referencing the way that a lattice structure is inspired by the cellular and crystal structures seen in nature.

 

Stiffness/modulus: The stiffness, or modulus, of the lattice refers to the force required to deform its structure. The modulus is typically defined for small deformations when the lattice response is fully elastic.

 

Buckling response: The buckling response describes the way that a lattice structure yields, and depends upon the structural instability of lattice elements as they deform. Not all lattice structures exhibit buckling – and buckling is not always a desirable feature.

 

Energy dissipation: The energy dissipation of a lattice structure refers to its ability to absorb energy while it is being deformed.

Example types of 3D printed lattice structure

Simple cubic 3D lattice structure

This Simple Cubic lattice has a unit cell size of 7.5 mm and a truss width of 2 mm. The modulus is 0.72 MPa.

 

Simple cubic

 

Buckling response: This structure of the Simple Cubic lattice exhibits buckling instability. After a strain of about 0.05, the modulus is constant at a stress plateau of 25 kPa. Additional deformation does not increase the modulus.

 

Energy dissipation: The Simple Cubic lattice has an inelastic buckling behavior which produces a different response when it is being loaded and unloaded. The inelastic behavior can be used for many purposes, including energy dissipation.

 

Applications: The buckling response of this Simple Cubic lattice produces a force threshold that makes it a good candidate for personal protection applications and for shielding sensitive components. This lattice type is also effective for filling gaps between components in assemblies.

Kelvin cell 3D lattice structure

This Kelvin cell lattice has a unit cell size of 10 mm and a truss width of 2 mm. The modulus is 0.44 MPa.

 

Kelvin

 

Buckling response: Unlike the Simple Cubic lattice, the Kelvin cell lattice structure has a low buckling point, meaning that its beams stretch in response to force. The Kelvin cell lattice does not have a plateau and compresses continuously with a simple elastic stiffness until it is fully compacted.

 

Energy dissipation: The Kelvin cell lattice stores energy with its elastic deformation, and it returns to its original shape quickly, like a spring, when force is removed.

 

Applications: The Kelvin cell lattice is a good candidate for foam replacement in products under static compression such as seat cushions or body pads. With its intricate hexagonal cells, the Kelvin cell lattice is quite visually striking, making it an option for aesthetic and fashion applications.

Body-Centered 3D lattice structure

This Body-Centered lattice has unit cell size of 10 mm and a truss width of 2 mm. The modulus is 0.07 MPa.

 

Body Centered

 

Buckling response: The Body-Centered lattice structure has a stretching response, meaning that it responds with increasing force per unit displacement until fully compacted. Its modulus is much lower compared to the Simple Cubic lattice, and it does not have a plateau stress.

 

Energy dissipation: Like the Kelvin unit, the Body-Centered lattice stores energy with its elastic deformation and returns to its original shape much like a spring when force is removed.

 

Applications: With its high strain elastic response, the Body-Centered lattice is a good candidate for foam replacement in products under static compression. The angled struts pointing towards the center of the cell make its response even and consistent.

 

Body-Centered Cubic (BCC) 3D lattice structure

The Body-Centered Cubic (BCC) lattice combines the Body-Centered lattice and Simple Cubic lattice in a single structure. This lattice has a unit cell size 7.5 mm, and a truss width 1 mm. The modulus is 0.23 MPa – which is higher than the Simple Cubic and Body-Centered Cubic lattices listed above.

 

BCC

 

Buckling response: Since the BCC lattice combines two types of 3D printed lattice, its response is a combination of both. This lattice buckles like the Simple Cubic lattice with a plateau stress (0.12 MPa) but has a more stable post-buckling behavior.

 

Energy dissipation: Because the BCC lattice combines both an elastic and a buckling response, it is possible to adjust energy storage and dissipation to serve specific applications.

 

Applications: The BCC lattice is particularly useful for applications that benefit from a tailored elastic and buckling response. It also works well when a product requires energy dissipation with a more stable response than the pure buckling seen in the Simple Cubic lattice.

Make new things possible with Fast Radius

The four structures highlighted above only scratch the surface of what is possible with an elastomeric 3D lattice structure design. To learn more, explore our case studies and find out how companies like Rawlings and Steelcase created innovative new products using 3D printed lattice structures. If you’re ready to begin your own 3D printing project, contact us today and make your next project possible.

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